Package io.grpc

Interface ClientInterceptor

  • All Known Implementing Classes:

    public interface ClientInterceptor
    Interface for intercepting outgoing calls before they are dispatched by a Channel.

    Implementers use this mechanism to add cross-cutting behavior to Channel and stub implementations. Common examples of such behavior include:

    • Logging and monitoring call behavior
    • Adding metadata for proxies to observe
    • Request and response rewriting

    Providing authentication credentials is better served by CallCredentials. But a ClientInterceptor could set the CallCredentials within the CallOptions.

    The interceptor may be called for multiple calls by one or more threads without completing the previous ones first. Refer to the ClientCall.Listener docs for more details regarding thread safety of the returned listener.

    • Method Detail

      • interceptCall

        <ReqT,​RespT> ClientCall<ReqT,​RespT> interceptCall​(MethodDescriptor<ReqT,​RespT> method,
                                                                      CallOptions callOptions,
                                                                      Channel next)
        Intercept ClientCall creation by the next Channel.

        Many variations of interception are possible. Complex implementations may return a wrapper around the result of next.newCall(), whereas a simpler implementation may just modify the header metadata prior to returning the result of next.newCall().

        next.newCall() must not be called under a different Context other than the current Context. The outcome of such usage is undefined and may cause memory leak due to unbounded chain of Contexts.

        method - the remote method to be called.
        callOptions - the runtime options to be applied to this call.
        next - the channel which is being intercepted.
        the call object for the remote operation, never null.